Remedies for a Fungus on a Rose Bush

Preventive Practices

• Plant roses where they will get a minimum of six hours of direct sun. Don't let other plants or other roses crowd them, as good air circulation is vital in preventing fungus diseases. Plant them in soil that has been amended with rich compost and water them deeply once a week, applying water to the base of the plant. Mulch to keep weeds at bay and moisture levels even. Begin a preventive spray program in spring, following package directions. Use organic fungicides containing copper or sulfur or a synthetic fungicide such as Funginex.

Blackspot

• Round black spots on leaves and stems are the symptom of this fungus disease. The spots often have a yellow circle around them. The leaves die and fall off. The fungus is spread by water, so avoid overhead watering and clean up any fallen foliage so spores don't splash onto the rest of the plant.

Powdery Mildew and Rust

• Mildew is gray or white and fuzzy. It grows on the leaf surface and causes young leaves to curl up, turn purple and drop off. It also affects buds, which don't open. Mildew spreads on the wind and develops quickly during wet or humid weather. Rust is characterized by powdery orange lesions on plant leaves and stems. It thrives in cool, wet weather.

Botrytis

• Stems and buds affected by botrytis turn dark brown or black, shrivel, droop and decay. Unopened buds, as well as opened flowers, may quickly become covered with a gray fungal fuzz. The fungus infects roses when water remains on leaves or buds, so it is most active in wet weather or when roses are watered with a sprinkler.